1. Field of the Invention
The present invention relates to apparatus for propelling a line through conduits to expedite the process of stringing electrical wires through the conduits. More particularly, but not by way of limitation, the present invention relates to an apparatus for propelling a line through conduits that is hand held, connects easily to a source of pressurized gas, and utilizes a heavy duty line which may be quickly and easily rewound for reuse.
2. Description of the Related Art
The safe transfer of electrical power along electrical wires requires complete insulation of the wires to prevent shorts form occurring. Shorting of the wires must be avoided because shorts pose a fire hazard, present the danger of electrocution to a person contacting the shorted wires, and, at a minimum, cause damage to electronic equipment receiving power through the wires. Typically, electrical wires are encased in rubberized insulation to prevent their shorting. However, that type of insulation cuts easily resulting in the exposure of the wires. Thus, additional methods of protecting electrical wires have been developed. One such method consists of stringing the electrical wires through protective conduits. Unfortunately, the process of actually running the electrical wires through the conduits is tedious as well as time and labor intensive which greatly increases the cost using protective conduits. Accordingly, devices designed to reduce the time and effort required to string electrical wires through conduits have been invented.
U.S. Pat. No. 979,899 issued on Dec. 27, 1910 to Steigleder and U.S. Pat. No. 443,823 issued on Dec. 30, 1890 to Cope both disclose early line threading devices. Those devices include a nozzle connected to a source of compressed air via a flexible tube. Positioned at the exit of the nozzle is a line carrier which connects to a spool of line. In operation, the line carrier is placed within the conduit with the nozzle placed over the conduit inlet. The compressed air source then delivers the compressed air into the conduit via the tube and nozzle to blow the line carrier through the conduit. As the line carrier travels through the conduit, it pulls the line from the spool and into the conduit.
U.S. Pat. No. 3,837,624 issued on Sep. 24, 1974 to Dandurand and U.S. Pat. No. 3,301,531 issued on Jan. 31, 1967 to Corsiglia both disclose similar devices. Those systems employ similar nozzles, flexible tubes, and line carriers connected to a spool of line. However, both devices employ an electrically operated air blower to propel the line carrier through the conduit rather than a source of compressed air. Alternatively, U.S. Pat. No. 3,119,600 issued on Jan. 28, 1964 to Bitter discloses the use of a vacuum cleaner to pull the line carrier and line through the conduit to the vacuum cleaner nozzle.
Although the above devices function adequately to install electrical wires within conduits, they suffer from several disadvantages. First, the sources which propel or pull the line carrier through the conduit are inadequate for conduits used today. Specifically, those sources simply have insufficient power to propel or pull the line carrier all the way through conduit, particularly when the conduit includes many turns. Second, the above devices are bulky making them difficult to transport to job sites and also to use in small spaces. For example, the bulky devices disclosed in the above references would be difficult if not impossible to use in a crawl way or attic. Furthermore, the large nozzles do not adequately fit within some junction boxes (e.g., shallow 2".times.4" junction boxes) or other close quarters.
U.S. Pat. No. 4,043,537 issued on Aug. 23, 1977 to Russo, Jr. and U.S. Pat. No. 3,689,031 issued on Sep. 5, 1972 to Ruddick, et al. disclose devices which offer more portability. Russo, Jr. discloses an apparatus for installing a pull line in conduits which includes a tubular body connecting a valve to a line dispensing air chamber. A reel mounts on the tubular body to supply line to a line carrier via the line dispensing air chamber. The valve connects to an air supply tank to regulate the delivery of air through the tubular body and the line dispensing air chamber to the line carrier. Thus, after the line dispensing air chamber is fitted over a conduit and the valve activated, compressed air forces the line carrier through the conduit thereby pulling line from the reel.
Ruddick, et al. disclose an angled nozzle that includes a head formed integrally with a body. The body includes an inlet which allows connection to either a compressed gas bottle or an air blower. The head includes an inlet that allows line to be strung from a spool through the head to a line carrier positioned outside the outlet from the head. After the line carrier is placed within the conduit and the nozzle over the conduit, the valve to the compressed gas bottle is opened or the air blower is turned on to propel the line carrier through the conduit.
The above devices operate adequately in most instances to install pull lines in conduit, however, they also experience the same disadvantages as the air blower-type devices. That is, they are bulky devices that offer problems when used in small places. Specifically, the long tubular construction of their air delivery apparatus makes their use in closed spaces awkward and often impossible.
Furthermore, their construction does not allow their use with high pressure compressed gas sources (e.g., CO.sub.2 compressed to 1800 psi), and the compressed gas sources which are employed provide insufficient pressures to propel the line carrier through conduits having many turns. With respect to Russo, Jr., the disclosed reel cannot dispense line fast enough to allow its use with high pressure compressed gas sources. Essentially, the reel does not unspool line quickly enough to keep pace with the line carrier as the high pressure compressed gas propels it through the conduit. As a result, the line will bind within the reel causing it to break. Similarly, the separate spool utilized in Ruddick, et al. is not designed to dispense line at a rate necessary to allow its use with high pressure compressed gas sources. Accordingly, neither of the above device can be employed to install pull lines through long lengths of conduit.
U.S. Pat. No. 4,726,564 issued on Feb. 24, 1988 to Lynn and U.S. Pat. No. 3,927,866 issued on Dec. 23, 1975 to Linquist disclose gun-type hand held pull line installing devices. Linquist discloses a pneumatic blow gun which includes a main body formed integrally with a handle. A guide resides within the handle to provide an inlet for the line into the barrel of the main body. The line carrier resides within the barrel and connects to the line. The line itself is supplied from an ordinary spool residing separate from the pneumatic blow gun. The handle connects to an air blower and includes a passage way to provide pressurized air into the barrel of the main body. Thus, in use, after the barrel is inserted into the conduit and the air blower activated, air travels through the handle into the barrel of the main body to propel the line carrier from the barrel into and through the conduit. However, as previously described, the use of an air blower provides insufficient air pressure to propel the line carrier through any significant length of conduit or through a conduit having many turns.
Lynn discloses a pull line installing device that includes a canister for holding a spool which mounts to a housing having a handle. Line from the spool runs through the housing and out an outlet where it connects to a line carrier. The housing handle connects to a pressurized gas source and includes a passageway to deliver the pressurized gas into the housing. Thus, after the line carrier is inserted into the conduit and the housing outlet is placed over the conduit, the flow of pressurized gas through the handle and housing will propel the line carrier through the conduit. However, similar to the reel disclosed in Russo, Jr., the spool placed within the canister of the Lynn reference cannot unspool fast enough to be used with high pressure compressed gas sources. If the device disclosed in Lynn were connected to a high pressure source of compressed gas, the line would bind along the spool thereby preventing the line carrier and line from being propelled through the entire length of the conduit.
Accordingly, any device which is both hand held for use in small, closed spaces and connects to a high pressure compressed gas source to allow the propelling of a line carrier through any conduit is highly desirable.